Chip-sized diode lasers with ultra-narrow spectral linewidth are of high interest for many applications, e.g. for phase encoding in optical communications and precision metrology. Recently, a record-narrow intrinsic linewidth of 290 Hz was achieved with hybrid integration of an InP semiconductor optical amplifier (SOA) and a low-loss dielectric waveguide feedback circuit with a Vernier spectrally selective feedback filter that significantly extends the on-chip cavity length. However, increasing the cavity length also reduces the cavity mode spacing, which causes undesired instabilities in the form of mode hops and power fluctuations when tuning the laser wavelength.

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